1. Field of the Invention
This invention relates to a mounting structure for mounting a case member to a functional machinery body such as an engine.
2. Description of the Related Art
An overhead cam-type engine, for example, includes a timing chain disposed on a lateral portion of the engine body for transmitting the engine power to the valve system, and the timing chain is covered by a chain case as a case member. The chain case is affixed to the engine body with its circumferential portion, and accommodates the timing chain in its inner cavity.
For example, Japanese Patent Laid-Open Publication No. hei 7-83069 discloses a chain case of a V-type engine. As shown in FIG. 9, the chain case 01 of the V-type engine is disposed on a lateral portion of an engine body like a cylinder block or a cylinder head. The chain case 01 has boltholes 02 substantially equally space along the circumferential portion, and it is affixed to the engine body by means of these boltholes 02. The chain case 01 also has a plurality of fastening boss portions 03 at predetermined positions in a central region, and boltholes 04 are formed through these fastening boss portions 03.
In this manner, the chain case 01 is fastened with bolts to the engine body at the plurality of fastening boss portions 03 in the central region not only along its circumferential portion such that the central region is integrally affixed to improve the rigidity. However, since the central region of the chain case 01 is fastened to the engine only locally at the fastening boss portions 03, rigidity of the entire central region cannot be enhanced unless a lot of such fastening boss portions 03 are formed to fix the central region of the chain case 01 to the engine body at many positions. The use of such a lot of fastening boss portions invites a complicated shape of the chain case and the need of a corresponding large number of fastening means such as bolts, which makes mounting of the chain case annoying.
It is therefore an object of the invention to provide a case member mounting structure that can improve the rigidity of a central region of a case member and can thereby minimize vibrations while facilitating its mounting with fewer fastening means.
To accomplish the above-mentioned object, according to the invention, there is provided a case member mounting structure for mounting a case member to a machinery body, comprising:
outer edge fastening means for fastening an outer edge region of the case member to the machinery body; and center fastening means for fastening a central region of the case member to the machinery body, the center fastening means including: a plurality of central fastener elements formed on an inner surface of the case member; and a raised connection wall connecting the central fastener elements, the case member being mounted to the machinery body by putting the connection wall and the central fastener elements in abutment with the machinery body.
In this manner, since the connection wall projecting from the inner wall surface of the case member to connect the central fastener elements, together with these central fastener elements, get in abutment with the machinery body, the case member is enhanced in rigidity by the fixture of its central region to the machinery body, thereby to prevent vibrations of the central region and noise thereof.
The structure using the abutment of the connection wall connecting the central fastener element with the machinery body contributes to simplifying the shape of the case member without the need of using a number of central fastening portions. It results in the need of fewer fastening means and making the assembly easier. Further, the connection wall also enhances the rigidity of the fastening portions and additionally enhances the fastening rigidity of the case member.
The connection wall is preferably annular. A through hole may be formed in the region inside the annular connection wall and may be used as means for mounting another member to the machinery body.
Because the case member is affixed by putting the annular connection wall in the central region of the case member in abutment with the machinery body, the structure is enhanced in rigidity, and vibrations of the central region can be prevented effectively.
The through hole made in the region inside the annular connection wall of the case member contributes to reducing the weight. At the same time, since the through hole can be used to mount the other member to the machinery body, it contributes to efficient use of the space. The other member can be detachably mounted in the machinery body without the need of removing the case member.
According to the invention, there is further provided a case member mounting structure for mounting a chain case to an engine body, comprising: outer edge fastening means for fastening an outer edge region of the chain case to the engine body; and center fastening means for fastening a central region of the chain case to the engine body, the center fastening means including: a plurality of central fastener elements formed on an inner surface of the chain case; and a raised connection wall connecting the central fastener elements, the case member being mounted to the machinery body by putting the connection wall and the central fastener elements in abutment with the machinery body.